Sensors are often utilized in association with internal combustion engines to measure operating parameters and constituents of a resulting feed stream. For example, an exhaust gas sensor in a control system of an internal combustion engine can be used to measure the parameter of air/fuel ratio, CO, CO2, NOx, etc. It is important to determine the gas concentration of exhaust gas in order to control the emission of an automotive engine. A control system can then use this information to control the engine parameters and thereby allow for minimum emissions.
An engine controller can then employ the air/fuel ratio information to control the feed stream that flows through the engine and into an after treatment device, such as a catalytic converter. A properly controlled gas feed stream is important for the complete operation of the exhaust after treatment and during light-off and steady-state warmed-up operations of the utilized control system.
Construction of a current sensor element can take place in the context of a planar-type (e.g., thin and long ceramic) substrate, which protrudes externally from the gas sensor housing for measuring gas concentration. Since the configuration is planar and thinner, the possibility of breakage due to vibration and mechanical shock is very high
It is known that the control of burning associated with an internal combustion engine is a function of the concentration of air-fuel ratio contained in exhaust gases. The concentration of the NOx and the air-fuel ratio is effective in providing energy savings and emission control capabilities. In gas sensor configurations suitable for measuring the concentration of oxygen or other gases like CO, NOx, CO2, etc., in exhaust gases, a solid electrolyte body constructed from zirconia or metal oxide semiconductor (MOS) based gas sensors can be utilized. This type of gas sensor, however, in order to be effective, must be reduced in size, while maintaining efficient production costs and improving its durability and reliability. These factors are difficult to achieve.
In order to sense gas concentration, such as O2, NOx etc., a gas sensor element should be operated at high temperature. For example, a zirconia sensor for measuring oxygen, should be maintained at 650 deg C. An electric power circuit controls the temperature of the sensor element. Designing the sensor element with small size is important in order to reduce power required to maintain the sensor at this temperature.
It is believed that a solution to overcoming these problems involves the implementation of an improved sensor apparatus, which can be efficiently fabricated at a low cost for automotive exhaust gas applications.